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Kupreanof


Facts

  • Official Name: Mount Kupreanof
  • Seismically Monitored: No
  • Color Code: YELLOW
  • Alert Level: ADVISORY
  • Elevation: 1895m (6217ft)
  • Latitude: 56.0126
  • Longitude: -159.7912
  • Smithsonian VNum: 312060
  • Pronunciation:
  • Nearby Towns:
    • Ivanof Bay 14 mi (22 km) SE
    • Perryville 26 mi (42 km) SE
    • Chignik Lake 43 mi (69 km) NE
    • Chignik Lagoon 53 mi (85 km) NE
    • Sand Point 54 mi (87 km) SW

    Distance from Anchorage: 505 mi (813 km)

Description

From Wood and Kienle (1990) [1] : "The Stepovak Bay group is a chain of five volcanoes at the southwest end of a N40E oriented linear segment of the Aleutian arc on the Alaska Peninsula. This same segment includes the better known Veniaminof and Aniakchak calderas. Three of the Stepovak Bay volcanoes (2, 4, and Kupreanof) have clearly had Holocene eruptions, resulting in three small debris flows filling late Pleistocene glacial valleys, and a small cinder cone and associated lava flow. The other two volcanoes (1 and 3) do not show unmistakable evidence of Holocene activity. They have ice-filled summit craters 500 m (1) and 300 m (3) in diameter that may be late Pleistocene age. These volcanoes have contributed to extensive late Tertiary and Quaternary lava flows, some extending near sea level.
"Kupreanof is the largest and best known volcano of the group. In 1982, reconnaissance mapping located the three southernmost volcanoes. Later work further delineated these three, and located an additional center (4). Mapping and K-Ar dating indicate the area has been the locus of voluminous volcanic activity for approximately the last 4 million years. A fumarole occurs at Kupreanof volcano; another has been reported on volcano 4. Air photos from the late 1940s also suggest the presence of a fumarole on volcano 1.
"Northwest of the line of volcanoes a projected fault vertically offsets the volcanoes from flows that are related to the early history of the centers. These flows, which dip away from the centers, yield K-Ar ages between 3.9 and 1.7 Ma. Along the trend, and 7 to 12 km southwest of the volcanoes, is another area of early (?) Quaternary flows possibly related to a yet unrecognized center; outcrops of hypabyssal rocks in a snowfield among these flows may be this center. The group of volcanoes overlies sedimentary rocks of Oligocene to late Miocene age; the southern centers also overlie thick tuff deposits of uncertain but presumably late Tertiary or early Quaternary age."

References Cited

[1] Volcanoes of North America: United States and Canada, 1990

Wood, C. A., and Kienle, Juergen, (eds.), 1990, Volcanoes of North America: United States and Canada: New York, Cambridge University Press, 354 p.

Current Activity

May 12, 2026, 9:01 am

Seismic activity and volcanic gas emissions increased over the past few months and now continue at elevated levels at Mount Kupreanof. This activity is likely caused by a magmatic intrusion beneath the volcano. The Alaska Volcano Observatory (AVO) is therefore increasing the Aviation Color Code to YELLOW and the Volcano Alert Level to ADVISORY in response to this sustained volcanic unrest. 

 

Summary of activity and hazards 

  • Seismicity was first detected in February 2026 and has increased in recent months, with earthquakes as large as magnitude 3.1 detected. 
  • Sulfur dioxide (SO2) emissions were detected beginning on April 4 with emission rates of ~100 to 1,000 tons per day, which are well above the background rate of <100 tons per day. 
  • These signals likely indicate a magmatic intrusion beneath Mount Kupreanof. 
  • AVO is therefore increasing the Aviation Color Code to YELLOW and the Volcano Alert Level to ADVISORY in response to this sustained volcanic unrest. 
  • Data do not suggest an eruption is imminent and further signs of increased unrest would be expected prior to eruption. 
  • There is no local monitoring network at Mount Kupreanof. Seismicity is detected using only regional stations, which limits detection of smaller events (magnitudes <2) and results in large location errors. 

 

For more information: 

Recent Updates

Color Code Timeline

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Before an eruption

Ashfall & Preparedness Information

During and After an Eruption

Other Useful Links

Ash Forecasting

Mathematical models developed by the USGS forecast various aspects of how a volcanic ash plume will interact with wind—where, how high, and how fast ash particles will be transported in the atmosphere, as well as where ash will fall out and accumulate on the ground. AVO runs these models when a volcano is restless by assuming a reasonable hypothetical eruption, to provide a pre-eruptive forecast of areas likely to be affected. During an ongoing eruption, AVO will update the forecast with actual observations (eruption start time and duration, plume height) as they become available.

View the current airborne ash cloud models for Kupreanof

Ashfall thickness forecast

The Ash3d model was developed by the USGS to forecast how a volcanic ash plume will interact with wind and where ash will fall out and accumulate on the ground. AVO runs these models twice daily when a volcano is restless by assuming a reasonable hypothetical eruption altitude and duration. The map shows the model results of ashfall thickness for areas that are likely to be affected, if one were to occur. During an ongoing eruption, AVO will update the forecast with actual observations (eruption start time and duration, plume height) as they become available, and these plots will be automatically updated. The National Weather Service Anchorage Forecast Office will issue the official ashfall warning product and post them at weather.gov/afc

THESE PRODUCTS MAY NOT BE CURRENT.

During an actual eruption, see National Weather Service forecasts of ashfall:https://weather.gov/afc.

Ashfall Forecast

Click on the X on the graphic (upper right) to expand the map to show the map legend.

Ashfall Start Time

This map shows the modeled estimate of the time it would take for ashfall to begin following an eruption. It corresponds to the ashfall thickness forecast map shown above. This map uses the start time of either the twice-daily hypothetical model runs (time shown in the legend) or the actual eruption start time (if one were to occur). In the case of an actual eruption, the National Weather Service Anchorage Forecast Office will issue the official ashfall warning product that includes the ashfall start time and post them at weather.gov/afc

THESE PRODUCTS MAY NOT BE CURRENT.

During an actual eruption, see National Weather Service forecasts of ashfall:https://weather.gov/afc.

Ashfall Start Times Forecast

Click on the X on the graphic (upper right) to expand the map to show the map legend.
× Instrument data